I've sadily had be in the room where a few animals were put down over my life.
The pricy vet drug was great. My dog felt no pain. Died in a millisecond. I died a bit that day too. The worse pain I have ever felt was over a pet.
My point is my Humane Society used a drug that slowly killed the animal. The animal did not look content. She looked at me, like "What's going on?". It wasen't my animal, but I felt it's misery. The only reason I was there is the owner couldn't handle the prolonged death. It was a good 8 plus minutes of dying.
My point is I don't know if the Humane Society purposely used a drug that didn't kill the animal immediately so the family could spend time with a dying pet. I don't know why they didn't use a drug that would stop the heart completely?
The horrid reason these dogs were put down was due to Section 8 housing laws. A busybody in the complex didn't like my friend who fell on hard times, and was trying to get her to move in abusive verbal ways. This horrid human just didn't like my friend, and had pull at the housing complex. She turned the dogs into Sec. 8 authorities for being a few pounds over 25. My friend put the dogs down. I still recall her asking me if by putting the dogs down was she being egocentric. I didn't say anything because she was literally living in a beach parking lot a few weeks before.
(Sorry about going on, and on. The death of any animal just tears me to pieces. Oh yea, I looked at the 42 page Section 8 lease. Yes---42 pages of "You can't do this, and you can't do that." My main point was I feel the Humane Society should use the most effective, fast acting, drugs available when they put an animal down.)
Europe imposed strict export controls on it and other drugs in 2014, but I don't think vetinary supply has been affected.
Anyway, I've been a vegetarian since not long after seeing that, going on 25 years now. I can understand and sympathise with feeling as you did. I understand but don't sympathise with the way your colleagues left the dirty work to you, very hypocritical of them. I've known a few vegetarians like that, it's more about their personal disgust and hence, comfort, than it is about anyone else's suffering. They're also the most fickle, in my experience, hunger will soon overcome less important emotions, like notions formed as child. They're the ones you'll hear saying “I was vegetarian for years but one day I was famished and all I had available was a burger… never looked back”.
You have principles they are yet to know.
[1] http://www.gutenberg.org/files/153/153-h/153-h.htm#chap10
I would say, no healthy animal wants to die.
Related... the silence of the lambs thing I witnessed first hand. A bunch of sheep taken off to be slaughtered, standing in complete silence. Welsh sheep are never silent, so it spooked me a lot. No visual cues as to their impending doom, yet they all stood there like ghosts.
This doesn't mean that any pig could articulate "I'm going to die". That isn't necessary. Nearly every ungulate (maybe not moose?) has a built-in mortal fear ready to surface at any time. New events, or repeated events with bad associations, bring out that fear. It takes a great deal of training to relax that.
The knackerman who deal with the last pony was so good at his job, it made what was a truly traumatic experience so much more bearable. I had walked around with Tim (the pony in question) after the vet had been and made him as comfortable as possible, and he had been leaning on me (he was in his twenties and I'd known him since he was a 3 month or so old foal).
When the time came to say goodbye, he was dealt with appropriately and passed away seemingly painlessly (the vet gave a lethal injection after a heavy sedative which saw him fall onto the floor pretty quickly). The knackerman left us time to say goodbye, and ensured that Tim's body was removed quickly and neatly, without us needing to see it happen. Moving an animal that weighs over a ton is clearly not easy, and it was done professionally and quickly. It was a relief to see him dealt with in a respectful manner, and was already a pretty horrible day was made much better by his professional manner and quick service.
I think jobs like these are so easily forgotten by people who don't have to deal with this sort of thing on a day-to-day (or even year-to-year) basis.